Earnings (Loss) Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0.4	0	0.4
Computations of basic and diluted earnings per share for income from continuing operations
Net income	$ 64.3	$ 29.4	$ 136.6	$ 68.0
Add: Loss from discontinued operations	1.5	20.3	9.3	40.5
Income from continuing operations	$ 65.8	$ 49.7	$ 145.9	$ 108.5
Weighted-average shares outstanding - basic	49.7	50.6	50.0	50.8
Effect of diluted securities attributable to stock-based payments	0.8	0.7	0.8	0.7
Weighted-average shares outstanding - diluted	50.5	51.3	50.8	51.5
Earnings per share:
Income from continuing operations, Basic	$ 1.32	$ 0.98	$ 2.92	$ 2.13
Loss from discontinued operations, Basic	$ (0.03)	$ (0.40)	$ (0.19)	$ (0.79)
Net income (loss), Basic	$ 1.29	$ 0.58	$ 2.73	$ 1.34
Income from continuing operations, Diluted	$ 1.30	$ 0.97	$ 2.87	$ 2.11
Loss from discontinued operations, Diluted	$ (0.03)	$ (0.40)	$ (0.18)	$ (0.79)
Net income (loss), Diluted	$ 1.27	$ 0.57	$ 2.69	$ 1.32